The invention relates to liquid crystalline (meth)acrylates suitable for dental and medical applications, as well as for optical, electrooptical application such as in liquid-crystal displays. The invention provides (meth)acrylate compounds which are liquid below 50xc2x0 C., and are useful in compositions for treating natural teeth, such as dental restorative, cement, adhesive, primer, sealant and root canal filling compositions. The invention provides dental cement compositions and methods of using them for binding hard tooth material, metal and ceramic. The cement compositions include polymerizable ethylenically unsaturated monomers. The cements have superior adhesion to tooth without separately acid etching dentin or enamel. Compositions of the invention are useful as dental cements, liners, bases and restoratives. Compositions of the invention include less reactive diluent than prior art compositions. Compositions of the invention polymerize to form polymeric material having low or no residual monomer, preferably less than 1 percent residual monomer.
A series of acrylate, methacrylate or vinyl terminated compounds comprising a mesogenic or rigid rod-like moiety including (meth)acrylate terminated oligomers I and II with a mesogenic terephthaloyl ester moiety are disclosed by G. G. Barclay, C. K. Ober, Prog. Polym. Sci. 18 (1993) 899; D. J. Broer, G. N. Mol, Polym. Engng. Sci. 31 (1991) 625; R. A. M. Hikmet, J. Lub, J. A. Higgins, Polymer 34 (1993) 1736. 
p-Hydroxy benzoic ester moieties incorporated into vinyl terminated compounds III are disclosed by D. J. Broer, J. Lub, G. N. Mol, Macromol. 26 (1993) 1244. 
A diacrylate (wherein R is H) and a dimethacrylate (wherein R is CH3) having the formula IV which comprises a biphenylhydroxy moiety is disclosed by H. Litt Morton, Wha-Tzong Whang, Kung-Ti Yen, Xue-Jun Qian, in J. Polym. Sci., Part A,: Polym. Chem. 31 (1993) 183, Morton H. Litt U.S. Ser. No. 89-369205. 
Acetylene terminated aromatic ester having the formula V are described by E. P. Douglas, Polymer Prep. 34 (1993) 702. 
Methacrylates having the formula VI with a ridged rod-like moiety are disclosed in T. Shindo, T. Uryu, Liquid Crystals 15 (1993) 239). 
A vinyl terminated bishydroxybenzoate having formula VII which comprises spacers and exhibits relatively low phase transition temperatures only on cooling (n=11: i65n62sA47sB31k) and relatively narrow liquid crystalline phases, are disclosed by H. Anderson, F. Sahlen, and U. W. Gedde, A. Hutt, in Macromol. Symp. (1994) 339.
Mixtures of (meth)acrylates comprising liquid crystalline monomers, dimethacrylates (2,2-Bis-[p-(2-hydroxy-3-methacryloyloxypropoxy)-phenyl]-propane) and di(meth) acrylates comprising liquid crystalline monomers are described in EP 0379058.
However, the known liquid crystalline mono- or difunctional molecules have melting temperatures and liquid crystalline behavior at temperatures above 50xc2x0 C. (Table 1 below, page 25). An application of these molecules in the liquid crystalline phase require temperatures over their melting temperature (50 to 170xc2x0 C.). An application at room temperature is only possible in the solid state or in solution.
In accordance with the invention monomers are provided which are liquid at room temperature and which show liquid crystalline behavior at least between 20 and 40xc2x0 C. These liquid crystalline monomers are useful in dentistry, medicine, microelectronics and optoelectronics.
It is an object of the invention to provide a polymerizable compound within the scope of the general formula: 
wherein
R1 is a group of the general formula
xe2x80x94Axe2x80x94, xe2x80x94Axe2x80x94Y1xe2x80x94Bxe2x80x94, xe2x80x94Axe2x80x94Y1xe2x80x94Bxe2x80x94Y2xe2x80x94C
xe2x80x83or a steroidal moiety, preferably selected of the group of cholesteryl compounds, wherein
each A, B and C independently is a substituted or unsubstituted aromatic moiety having 6 to 24 carbon atoms, a substituted or unsubstituted heteroaromatic moiety having 2 to 24 carbon atoms or a substituted or unsubstituted cycloalkylene moiety having 5 to 30 carbon atoms, a substituted or unsubstituted alkylene moiety having 2 to 20 carbon atoms
each Y1 and Y2 independently is a covalent bond, OCO, Nxe2x95x90N, CHxe2x95x90N, Cxe2x95x90C, CO, O(CO)O, O, S, SO2, OCS, CH2xe2x80x94O, CH2S, 
xe2x80x83each L1 and L2 independently is a hydrogen, a alkylene having 1 to 20 carbon atoms or CN
R3 is a covalent bond or a substituted or unsubstituted alkylene having 1 to 20 carbon atoms, oxyalkylene having 1 to 20 carbon atoms, thioalkylene having 1 to 20 carbon atoms or a carboxyalkylene having 1 to 20 carbon atoms
R4 is hydrogen, a substituted or an unsubstituted alkyl having 1 to 20 carbon atoms, cycloalkyl having 5 to 12 carbon atoms, or aryl rest having 6 to 20 carbon atoms,
M is a mesogenic group of the general formula
xe2x80x94Axe2x80x94Z, xe2x80x94Axe2x80x94Y1xe2x80x94Bxe2x80x94Z, xe2x80x94Axe2x80x94Y1xe2x80x94Bxe2x80x94Y2xe2x80x94Cxe2x80x94Z
xe2x80x83or a steroidal moiety, preferably selected of the group of cholesteryl compounds, wherein
each A, B and C independently is a substituted or unsubstituted aromatic moiety having 6 to 24 carbon atoms, a substituted or unsubstituted heteroaromatic moiety having 2 to 24 carbon atoms or a substituted or unsubstituted cycloalkylene moiety having 5 to 30 carbon atoms
each Y1 and Y2 independently is a covalent bond, OCO, Nxe2x95x90N, CHxe2x95x90N, Cxe2x95x90C, CO, O(CO)O, O, S, SO2, OCS, CH2xe2x80x94O, CH2xe2x80x94S, 
xe2x80x83each L1 and L2 independently is a hydrogen, a alkylene having 1 to 20 carbon atoms or CN
Z is a hydrogen, halogen, CN, xe2x80x94OR, COOR, NO2, a halogen substituted or unsubstituted alkylene or alkenyl having 1 to 20 carbon atoms, a halogen substituted or unsubstituted oxyalkylene or oxyalkenyl having 1 to 20 carbon atoms, a halogen substituted or unsubstituted thioalkylene or thioalkenyl having 1 to 20 carbon atoms, a halogen substituted or unsubstituted carboxyalkylene or alkanoylenoxy having 1 to 20 carbon atoms,
X is a covalent bond, CO, NHCO, OCO,
n is an integer from 1 to 10.